I'm kind of late to the discussion, but this is something I love to talk about. I think that as long as people are going to buy these celebrity's books en mass then the industry will keep publishing them because they have no reason not to. If the publishing industry is making a lot of money off of those books they might be able to also take on new authors on a smaller scale because they know they can cover the cost.
An epidemic going on now is youtuber books. Every single big youtuber is coming out with their own life story, but I think that most of them are doing quite a bit of writing. None of their books seem particularly long, and they're probably padded with photos, so it's just my assumption.
Finally, going back to the original topic, I would rather have a ghostwriter write a celebrity's novel than the celebrities themselves because they probably don't have the time or the talent to do it themselves. If someone else is hired to write it than chances are they are going to be pretty good. People will always want to know more about celebrities so if, in this case, it is giving the publishing industry more money to support smaller authors, and giving ghostwriters (who might be struggling new authors as well) some exposure, then I am all for it. As long as they're being honest.